Inductive repeater coil for an implantable device

ABSTRACT

The present invention is a power and data transmission system for an implantable device. In particular, it is an inductive system with a passive repeater coil pair to improve efficiency of the device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 11/206,484, filed Aug. 17, 2005, which is a DivisionalApplication of U.S. patent application Ser. No. 09/515,373, filed Feb.29, 2000 now abandoned, which claims the benefit of U.S. ProvisionalApplication No. 60/125,873, filed Mar. 24, 1999.

TECHNICAL FIELD OF INVENTION

The present invention relates to electrical stimulation of the retina toproduce artificial images for the brain. It relates to electronic imagestabilization techniques based on tracking the movements of the eye. Itrelates to telemetry in and out of the eye for uses such as remotediagnostics and recording from the retinal surface.

The present invention also relates to electrical stimulation of theretina to produce phosphenes and to produce induced color vision. Thepresent invention relates to hermetically sealed electronic andelectrode units which are safe to implant in the eye.

BACKGROUND

Color perception is part of the fabric of human experience. Homer (c.1100 b.c.) writes of “the rosy-fingered dawn”. Lady Murasaki no Shikibu(c. 1000 a.d.) uses word colors (“purple, yellow shimmer of dresses,blue paper”) in the world's first novel. In the early nineteenth centuryThomas Young, an English physician, proposed a trichromatic theory ofcolor vision, based on the action of three different retinal receptors.Fifty years later James Clerk Maxwell, the British physicist and Hermannvon Helmholtz, the German physiologist, independently showed that all ofthe colors we see can be made up from three suitable spectral colorlights. In 1964 Edward MacNichol and colleagues at Johns Hopkins andGeorge Wald at Harvard measured the absorption by the visual pigments incones, which are the color receptor cells. Rods are another type ofphotoreceptor cell in the primate retina. These cells are more sensitiveto dimmer light but are not directly involved in color perception. Theindividual cones have one of three types of visual pigment. The first ismost sensitive to short waves, like blue. The second pigment is mostsensitive to middle wavelengths, like green. The third pigment is mostsensitive to longer wavelengths, like red.

The retina can be thought of a big flower on a stalk where the top ofthat stalk is bent over so that the back of the flower faces the sun. Inplace of the sun, think of the external light focused by the lens of theeye onto the back of the flower. The cones and rods cells are on thefront of the flower; they get the light which has passed through fromthe back of the somewhat transparent flower. The photoreceptor nervecells are connected by synapses to bipolar nerve cells, which are thenconnected to the ganglion nerve cells. The ganglion nerve cells connectto the optic nerve fibers, which is the “stalk” that carries theinformation generated in the retina to the brain. Another type ofretinal nerve cell, the horizontal cell, facilitates the transfer ofinformation horizontally across bipolar cells. Similarly, another typeof cell, the amacrine facilitates the horizontal transfer of informationacross the ganglion cells. The interactions among the retinal cells canbe quite complex. On-center and off-center bipolar cells can bestimulated at the same time by the same cone transmitter release todepolarize and hyperpolarize, respectively. A particular cell'sreceptive field is that part of the retina, which when stimulated, willresult in that cell's stimulation. Thus, most ganglion cells would havea larger receptive field than most bipolar cells. Where the response tothe direct light on the center of a ganglion cells receptive field isantagonized by direct light on the surround of its receptive field, theeffect is called center-surround antagonism. This phenomenon isimportant for detecting borders independent of the level ofillumination. The existence of this mechanism for sharpening contrastwas first suggested by the physicist Ernst Mach in the late 1800's. Moredetailed theories of color vision incorporate color opponent cells. Onthe cone level, trichromatic activity of the cone cells occurs. At thebipolar cell level, green-red opponent and blue-yellow opponentprocessing systems of the center-surround type, occur. For example, acell with a green responding center would have a annular surround area,which responded in an inhibiting way to red. Similarly there can bered-center responding, green-surround inhibiting response. The othercombinations involve blue and yellow in an analogous manner.

It is widely known that Galvani, around 1780, stimulated nerve andmuscle response electrically by applying a voltage on a dead frog'snerve. Less well known is that in 1755 LeRoy discharged a Leyden jar,i.e., a capacitor, through the eye of a man who had been blinded by thegrowth of a cataract. The patient saw “flames passing rapidly downward.”

In 1958, Tassicker was issued a patent for a retinal prostheticutilizing photosensitive material to be implanted subretinally. In thecase of damage to retinal photoreceptor cells that affected vision, theidea was to electrically stimulate undamaged retinal cells. Thephotosensitive material would convert the incoming light into anelectrical current, which would stimulate nearby undamaged cells. Thiswould result in some kind of replacement of the vision lost. Tassickerreports an actual trial of his device in a human eye. (U.S. Pat. No.2,760,483).

Subsequently, Michelson (U.S. Pat. No. 4,628,933), Chow (U.S. Pat. Nos.5,016,633; 5,397,350; 5,556,423), and De Juan (U.S. Pat. No. 5,109,844)all were issued patents relating to a device for stimulating undamagedretinal cells. Chow and Michelson made use of photodiodes andelectrodes. The photodiode was excited by incoming photons and produceda current at the electrode.

Normann et al. (U.S. Pat. No. 5,215,088) discloses long electrodes 1000to 1500 microns long designed to be implanted into the brain cortex.These spire-shaped electrodes were formed of a semiconductor material.

Najafi, et al., (U.S. Pat. No. 5,314,458), disclosed an implantablesilicon-substrate based microstimulator with an external device whichcould send power and signal to the implanted unit by RF means. Theincoming RF signal could be decoded and the incoming RF power could berectified and used to run the electronics.

Difficulties can arise if the photoreceptors, the electronics, and theelectrodes all tend to be mounted at one place. One issue is theavailability of sufficient area to accommodate all of the devices, andanother issue is the amount of power dissipation near the sensitiveretinal cells. Since these devices are designed to be implanted into theeye, this potential overheating effect is a serious consideration.

Since these devices are implants in the eye, a serious problem is how tohermetically seal these implanted units. Of further concern is theoptimal shape for the electrodes and for the insulators, which surroundthem. In one embodiment there is a definite need that the retinal deviceand its electrodes conform to the shape of the retinal curvature and atthe same time do not damage the retinal cells or membranes.

The length and structure of electrodes must be suitable for applicationto the retina, which averages about 200 microns in thickness. Based onthis average retinal thickness of 200 microns, elongated electrodes inthe range of 100 to 500 microns appear to be suitable. These elongatedelectrodes reach toward the cells to be activated. Being closer to thetargeted cell, they require less current to activate it.

In order not to damage the eye tissue there is a need to maintain anaverage charge neutrality and to avoid introducing toxic or damagingeffects from the prosthesis.

A desirable property of a retinal prosthetic system is making itpossible for a physician to make adjustments on an on-going basis fromoutside the eye. One way of doing this would have a physician's controlunit, which would enable the physician to make adjustments and monitorthe eye condition. An additional advantageous feature would enable thephysician to perform these functions at a remote location, e.g., fromhis office. This would allow one physician to remotely monitor a numberof patients remotely without the necessity of the patient coming to theoffice. A patient could be traveling distantly and obtain physicianmonitoring and control of the retinal color prosthetic parameters.

Another version of the physician's control unit is a hand-held,palm-size unit. This unit will have some, but not all of thefunctionality of the physician's control unit. It is for the physicianto carry on his rounds at the hospital, for example, to check onpost-operative retinal-prosthesis implant patients. Its extremeportability makes other situational uses possible, too, as a practicalmatter.

The patient will want to control certain aspects of the visual imagefrom the retinal prosthesis system, in particular, image brightness.Consequently, a patient controller, performing fewer functions than thephysician's controller is included as part of the retinal prostheticsystem. It will control, at a minimum, bright image, and it will controlthis image brightness in a continuous fashion. The image brightness maybe increased or decreased by the patient at any time, under normalcircumstances.

A system of these components would itself constitute part of a visualprosthetic to form images in real time within the eye of a person with adamaged retina. In the process of giving back sight to those who areunable to see, it would be advantageous to supply artificial colors inthis process of reconstructing sight so that the patient would be ableto enjoy a much fuller version of the visual world.

In dealing with externally mounted or externally placed means forcapturing image and transmitting it by electronic means or other intothe eye, one must deal with the problem of stabilization of the image.For example, a head-mounted camera would not follow the eye movement. Itis desirable to track the eye movements relative to the head and usethis as a method or approach to solving the image stabilization problem.

By having a method and apparatus for the physician and the technician toinitially set up and measure the internal activities and adjust these,the patient's needs can be better accommodated. The opportunity existsto measure internal activity and to allow the physician, using hisjudgment, to adjust settings and controls on the electrodes. Even theindividual electrodes would be adjusted by way of the electronicscontrolling them. By having this done remotely, by remote means eitherby telephone or by the Internet or other such, it is clear that aphysician would have the capability to intervene and make adjustment asnecessary in a convenient and inexpensive fashion, to serve manypatients.

SUMMARY OF INVENTION

The objective of the current invention is to restore color vision, inwhole or in part, by electrically stimulating undamaged retinal cells,which remain in patients with lost or degraded visual function arising,for example, from Retinitis Pigmentosa or Age-Related MacularDegeneration. This invention is directed toward patients who have beenblinded by degeneration of photoreceptors; but who have sufficientbipolar cells, or other cells acting similarly, to permit electricalstimulation.

There are three main functional parts to this invention. One is externalto the eye. The second part is internal to the eye. The third part isthe communication circuitry for communicating between those two parts.Structurally there are two parts. One part is external to the eye andthe other part in implanted within the eye. Each of these structuralparts contains two way communication circuitry for communication betweenthe internal and external parts.

The structural external part is composed of a number of subsystems.These subsystems include an external imager, an eye-motion compensationsystem, a head motion compensation system, a video data processing unit,a patient's controller, a physician's local controller, a physician'sremote controller, and a telemetry unit. The imager is a video camerasuch as a CCD or CMOS video camera. It gathers an image approximatingwhat the eyes would be seeing if they were functional.

The imager sends an image in the form of electrical signals to the videodata processing unit. In one aspect, this unit formats a grid-like orpixel-like pattern that is then ultimately sent to electronic circuitry(part of the internal part) within the eye, which drives the electrodes.These electrodes are inside the eye. They replicate the incoming patternin a useable form for stimulation of the retina so as to reproduce afacsimile of the external scene. In an other aspect of this inventionother formats other than a grid-like or pixel like pattern are used, forexample a line by line scan in some order, or a random but known order,point-by-point scan. Almost any one-to-one mapping between the acquiredimage and the electrode array is suitable, as long as the braininterprets the image correctly.

The imager acquires color information. The color data is processed inthe video data processing unit. The video data processing unit consistsof microprocessor CPU's and associated processing chips includinghigh-speed data signal processing (DSP) chips.

In one aspect, the color information is encoded by time sequences ofpulses separated by varying amounts of time; and, the pulse duration maybe different for various pulses. The basis for the color encoding is theindividual color code reference (FIG. 2 a). The electrodes stimulate thetarget cells so as to create a color image for the patient,corresponding to the original image as seen by the video camera, orother imaging means.

Color information, in an alternative aspect, is sent from the video dataprocessing unit to the electrode array, where each electrode has beendetermined to stimulate preferentially one of the bipolar cell types,namely, red-center green-surround, green-center-red-surround,blue-center-yellow-surround, or yellow-center-blue-surround.

An eye-motion compensation system is an aspect of this invention. Theeye tracker is based on detection of eye motion from the corneal reflexor from implanted coils of wire, or, more generally, insulatedconductive coils, on the eye or from the measurement of electricalactivity of extra-ocular muscles. Communication is provided between theeye tracker and the video data processing unit by electromagnetic oracoustical telemetry. In one embodiment of the invention,electromagnetic-based telemetry may be used. The results of detectingthe eye movement are transmitted to a video data processing unit,together with the information from the camera means. Another aspect ofthe invention utilizes a head motion sensor and head motion compensationsystem. The video data processing unit can incorporate the data of themotion of the eye as well as that of the head to further adjust theimage electronically so as to account for eye motion and head motion.

The internal structural part which is implanted internally within theeye, is also composed of a number of subsystems. These can becategorized as electronic circuits and electrode arrays, andcommunication subsystems, which may include electronic circuits. Thecircuits, the communication subsystems, and the arrays can behermetically sealed and they can be attached one to the other byinsulated wires. The electrode arrays and the electronic circuits can beon one substrate, or they may be on separate substrates joined by aninsulated wire or by a plurality of insulated wires. This is similarlythe case for a communication subsystem.

A plurality of predominately electronic substrate units and a pluralityof predominately electrode units may be implanted or located within theeye as desired or as necessary. The electrodes are designed so that theyand the electrode insulation conform to the retinal curvature. Thevariety of electrode arrays include recessed electrodes so that theelectrode array surface coming in contact with the retinal membrane orwith the retinal cells is the non-metallic, more inert insulator.

Another aspect of the invention is the elongated electrode, which isdesigned to stimulate deeper retinal cells by penetrating into theretina by virtue of the length of its electrodes. A plurality ofelectrodes is used. The elongated electrodes are of lengths from 100microns to 500 microns. With these lengths, the electrode tips can reachthrough those retinal cells not of interest but closer to the targetstimulation cells, the bipolar cells. The number of electrodes may rangefrom 100 on up to 10,000 or more. With the development of electrodefabrication technology, the number of electrodes might rage up to onemillion or more.

Another aspect of the invention uses a plurality of capacitiveelectrodes to stimulate the retina, in place of non-capacitiveelectrodes. Another aspect of the invention is the use of a neurotrophicfactor, for example, Nerve Growth Factor, applied to the electrodes, orto the vicinity of the electrodes, to aid in attracting target nervesand other nerves to grow toward the electrodes.

Hermetic sealing is accomplished by coating the object to be sealed witha substance selected from the group consisting of silicon carbide,diamond-like coating, silicon nitride and silicon oxide in combination,titanium oxide, tantalum oxide, aluminum nitride, aluminum oxide,zirconium oxide. This hermetic sealing aspect of the invention providesan advantageous alternative to glass coverings for hermetic seals, beingless likely to become damaged.

Another feature of one aspect of the structural internal-to-the-eyesubsystems is that the electronics receive and transmit information incoded or pulse form via electromagnetic waves. In the case whereelectromagnetic waves are used, the internal-to-the-eye implantedelectronics can rectify the RF, or electromagnetic wave, current anddecode it. The power being sent in through the receiving coil isextracted and used to drive the electronics. In some instances, theimplanted electronics acquire data from the electrode units to transmitout to the video data processing unit.

In another aspect the information coding is done with ultrasonic sound.An ultrasonic transducer replaces the electromagnetic wave receivingcoil inside the eye. An ultrasonic transducer replaces the coil outsidethe eye for the ultrasonic case. By piezoelectric effects, the soundvibration is turned into electrical current, and energy extractedtherefrom.

In another aspect of the invention, information is encoded by modulatinglight. For the light modulation case, a light emitting diode (LED) orlaser diode or other light generator, capable of being modulated, actsas the information transmitter. Information is transferred serially bymodulating the light beam, and energy is extracted from the light signalafter it is converted to electricity. A photo-detector, such as aphotodiode, which turns the modulated light signal into a modulatedelectrical signal, is used as a receiver.

Another aspect of the structural internal-to-the-eye subsystems of thisinvention is that the predominately electrode array substrate unit andthe predominately electronic substrate unit, which are joined byinsulated wires, can be placed near each other or in differentpositions. For example, the electrode array substrate unit can be placedsubretinally and the electronic substrate unit placed epiretinally. On afurther aspect of this invention, the electronic substrate unit can beplaced distant from the retina so as to avoid generating additional heator decreasing the amount of heat generated near the retinal nervesystem. For example, the receiving and processing circuitry could beplaced in the vicinity of the pars plana. In the case where theelectronics and the electrodes are on the same substrate chip, two ofthese chips can be placed with the retina between them, one chipsubretinal and the other chip epiretinal, such that the electrodes oneach may be aligned. Two or more guide pins with corresponding guidehole or holes on the mating chip accomplish the alignment.Alternatively, two or more tiny magnets on each chip, each magnet of thecorrect corresponding polarity, may similarly align the sub- andepiretinal electrode bearing chips. Alternatively, corresponding partswhich mate together on the two different chips and which in a fullymated position hold each other in a locked or “snap-together” relativeposition.

Now as an element of the external-to-the-eye structural part of theinvention, there is a provision for a physician's hand-held test unitand a physician's local or remote office unit or both for control ofparameters such as amplitudes, pulse widths, frequencies, and patternsof electrical stimulation.

The physician's hand-held test unit can be used to set up or evaluateand test the implant during or soon after implantation at the patient'sbedside. It has, essentially, the capability of receiving what signalscome out of the eye and having the ability to send information in to theretinal implant electronic chip. For example, it can adjust theamplitudes on each electrode, one at a time, or in groups. The hand-heldunit is primarily used to initially set up and make a determination ofthe success of the retinal prosthesis.

The physician's local office unit, which may act as a set-up unit aswell as a test unit, acts directly through the video data processingunit. The remote physician's office unit would act over the telephonelines directly or through the Internet or a local or wide area network.The office units, local and remote, are essentially the same, with theexception that the physician's remote office unit has the additionalcommunications capability to operate from a location remote from thepatient. It may evaluate data being sent out by the internal unit of theeye, and it may send in information. Adjustments to the retinal colorprosthesis may be done remotely so that a physician could handle amultiple number of units without leaving his office. Consequently thisapproach minimizes the costs of initial and subsequent adjustments.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the invention will bemore apparent from the following detailed description wherein:

FIG. 1 a shows the general structural aspects of the retina colorprosthesis system;

FIG. 1 b shows the retina color prosthesis system with a structural partinternal (to the eye), with an external part with subsystems foreye-motion feedback to enable maintaining a stable image presentation,and with a subsystems for communicating between the internal andexternal parts, and other structural subsystems;

FIG. 1 c shows an embodiment of the retina color prosthesis system whichis, in part, worn in eyeglass fashion;

FIG. 1 d shows the system in FIG. 1 c in side view;

FIG. 2 a shows an embodiment of the color I coding schemata for thestimulation of the sensation of color;

FIG. 2 b represents an embodiment of the color I conveying method wherea “large” electrode stimulates many bipolar cells with the color codingschemata of FIG. 2 a;

FIG. 2 c represents an embodiment of the color II conveying method wherean individual electrode stimulates a single type of bipolar cell;

FIG. 3 a represents an embodiment of the telemetry unit including anexternal coil, an internal (to the eye) coil, and an internal electronicchip;

FIG. 3 b represents an embodiment of the telemetry unit including anexternal coil, an internal (to the eye) coil, an external electronicchip, a dual coil transfer unit, and an internal electrode array;

FIG. 3 c shows and acoustic energy and information transfer system;

FIG. 3 d shows a light energy and information transfer system;

FIG. 4 represents an embodiment of the external telemetry unit;

FIG. 5 shows an embodiment of an internal telemetry circuit andelectrode array switcher;

FIG. 6 a shows a monopolar electrode arrangement and illustrates a setof round electrodes on a substrate material;

FIG. 6 b shows a bipolar electrode arrangement;

FIG. 6 c shows a multipolar electrode arrangement;

FIG. 7 shows the corresponding indifferent electrode for monopolarelectrodes;

FIG. 8 a depicts the location of an epiretinal electrode array locatedinside the eye in the vitreous humor located above the retina, towardthe lens capsule and the aqueous humor;

FIG. 8 b shows recessed epiretinal electrodes where the electricallyconducting electrodes are contained within the electrical insulationmaterial; a silicon chip acts as a substrate; and the electrodeinsulator device is shaped so as to contact the retina in a conformalmanner;

FIG. 8 c is a rendering of an elongated epiretinal electrode array withthe electrodes shown as pointed electrical conductors, embedded in anelectrical insulator, where an pointed electrodes contact the retina ina conformal manner, however, elongated into the retina;

FIG. 9 a shows the location of a subretinal electrode array below theretina, away from the lens capsule and the aqueous humor. The retinaseparates the subretinal electrode array from the vitreous humor;

FIG. 9 b illustrates the subretinal electrode array with pointedelongated electrode, the insulator, and the silicon chip substrate wherethe subretinal electrode array is in conformal contact with the retinawith the electrodes elongated to some depth;

FIG. 10 a shows a iridium electrode that comprises a iridium slug, aninsulator, and a device substrate where this embodiment shows theiridium slug electrode flush with the extent of the insulator;

FIG. 10 b indicates an embodiment similar to that shown in FIGS. 10/12a, however, the iridium slug is recessed from the insulator along itssides, but with its top flush with the insulator;

FIG. 10 c shows an embodiment with the iridium slug as in FIGS. 10/12 b;however, the top of the iridium slug is recessed below the level of theinsulator;

FIG. 10 d indicates an embodiment with the iridium slug coming to apoint and insulation along its sides, as well as a being within theoverall insulation structure;

FIG. 10 e indicates an embodiment of a method for fabricating and thefabricated iridium electrode where on a substrate of silicon an aluminumpad is deposited; on the pad the conductive adhesive is laid andplatinum or iridium foil is attached thereby; a titanium ring is placed,sputtered, plated, ion implanted, ion beam assisted deposited (IBAD) orotherwise attached to the platinum or iridium foil; silicon carbide,diamond-like coating, silicon nitride and silicon oxide in combination,titanium oxide, tantalum oxide, aluminum nitride, aluminum oxide orzirconium oxide or other insulator will adhere better to the titaniumwhile it would not adhere as well to the platinum or iridium foil;

FIG. 11 a depicts a preferred electrode where it is formed on a siliconsubstrate and makes use of an aluminum pad, a metal foil such asplatinum or iridium, conductive adhesive, a titanium ring, aluminum orzirconium oxide, an aluminum layer, and a mask;

FIG. 11 b shows an elongated electrode formed on the structure of FIG.11 a with platinum electroplated onto the metal foil, the mask removedand insulation applied over the platinum electrode;

FIG. 11 c shows a variation of a form of the elongated electrode whereinthe electrode is thinner and more recessed from the well sides;

FIG. 11 d shows a variation of a form of the elongated electrode whereinthe electrode is squatter but recessed from the well sides;

FIG. 11 e shows a variation of a form of the elongated electrode whereinthe electrode is a mushroom shape with the sides of its tower recessedfrom the well sides and its mushroom top above the oxide insulatingmaterial;

FIG. 12 a shows the coil attachment to two different conducting pads atan electrode node;

FIG. 12 b shows the coil attachment to two different conducting pads atan electrode node, together with two separate insulated conductingelectrical pathways such as wires, each attached at two differentelectrode node sites on two different substrates;

FIG. 12 c shows an arrangement similar to that seen in FIGS. 12/16 d,with the difference that the different substrates are very close with anon-conducting adhesive between them and an insulator such as aluminumor zirconium oxide forms a connection coating over the two substrates,in part;

FIG. 12 d depicts an arrangement similar to that seen in FIGS. 12/16 c;however, the connecting wires are replaced by an externally placedaluminum conductive trace;

FIG. 13 shows a hermetically sealed flip-chip in a ceramic or glass casewith solder ball connections to hermetically sealed glass frit and metalleads;

FIG. 14 shows a hermetically sealed electronic chip as in FIG. 18 withthe addition of biocompatible leads to pads on a remotely locatedelectrode substrate;

FIG. 15 shows discrete capacitors on the electrode-opposite side of anelectrode substrate;

FIG. 16 a shows an electrode-electronics retinal implant placed with theelectrode half implanted beneath the retina, subretinally, while theelectronics half projects above the retina, epiretinally;

FIG. 16 b shows another form of sub- and epi-retinal implantationwherein half of the electrode implant is epiretinal and half issubretinal;

FIG. 16 c shows the electrode parts are lined up by alignment pins or byvery small magnets;

FIG. 16 d shows the electrode part lined up by template shapes which maysnap together to hold the parts in a fixed relationship to each other;

FIG. 17 a shows the main screen of the physician's (local) controller(and programmer);

FIG. 17 b illustrates the pixel selection of the processing algorithmwith the averaging of eight surrounding pixels chosen as one element ofthe processing;

FIG. 17 c represents an electrode scanning sequence, in this case thepredefined sequence, A;

FIG. 17 d shows electrode parameters, here for electrode B, includingcurrent amplitudes and waveform timelines;

FIG. 17 e illustrates the screen for choosing the global electrodeconfiguration, monopolar, bipolar, or multipolar;

FIG. 17 f renders a screen showing the definition of bipolar pairs (ofelectrodes);

FIG. 17 g shows the definition of the multipole arrangements;

FIG. 18 a illustrates the main menu screen for the palm-sized test unit;

FIG. 18 b shows a result of pressing on the stimulate bar of the mainmenu screen, where upon pressing the start button the amplitudes A1 andA2 are stimulated for times t1, t2, t3, and t4, until the stop button ispressed;

FIG. 18 c exhibits a recording screen that shows the retinal recordingof the post-stimulus and the electrode impedance;

FIGS. 19 a-c show the physician's remote controller that has the samefunctionality inside as the physician's controller but with the additionof communication means such as telemetry or telephone modem; and

FIG. 20 shows the patient's controller unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is merely made for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

Objective

The objective of the embodiments of the current invention is a retinalcolor prosthesis to restore color vision, in whole or in part, byelectrically stimulating undamaged retinal cells, which remain inpatients with, lost or degraded visual function. Embodiments of thisretinal color prosthesis invention are directed toward helping patientswho have been blinded by degeneration of photoreceptors and other cells;but who have sufficient bipolar cells and the like to permit theperception of color vision by electric stimulation. By color vision, itis meant to include black, gray, and white among the term color.

General Description

Functionally, there are three main parts to an embodiment of thisretinal color prosthesis invention. See FIG. 1 a. FIG. 1 a is orientedtoward showing the main structural parts and subsystems, with a dottedenclosure to indicate a functional intercommunications aspect. The firstpart of the embodiment is external (1) to the eye. The second part isimplanted internal (2) to the eye. The third part is means forcommunication between those two parts (3). Structurally there are twoparts. One part is external (1) to the eye and the other part (2) isimplanted within the eye. Each of these structural parts contains twoway communication circuitry for communication (3) between the internal(2) and external (1) parts.

The external part of the retinal color prosthesis is carried by thepatient. Typically, the external part including imager, video dataprocessing unit, eye-tracker, and transmitter/receiver are worn as aneyeglass-like unit. Typical of this embodiment, a front view of oneaspect of the structural external part (1) of the color retinalprosthesis is shown in FIG. 1 c and a side view is shown in FIG. 1 d,(1). In addition, there are two other units which may be plugged intothe external unit; when this is done they act as part of the externalunit. The physician's control unit is not normally plugged into theexternal part worn by the patient, except when the physician isconducting an examination and adjustment of the retinal colorprosthetic. The patient's controller may or may not be normally pluggedin. When the patient's controller is plugged in, it can also receivesignals from a remote physician's controller which then acts in the sameway as the plug-in physician's controller.

Examining further the embodiment of the subsystems of the external part,see FIG. 1 b. These include an external color imager (111), aneye-motion compensation system (112), a head-motion compensation system(131), a processing unit (113), a patient's controller (114), aphysician's local controller (115), a physicians hand-held palm-sizepocket-size unit (130), a physician's remote controller (117), and atelemetry means (118). The color imager is a color video camera such asa CCD or CMOS video camera. It gathers an image approximating what theeyes would be seeing if they were functional.

An external imager (111) sends an image in the form of electricalsignals to the video data processing unit (113). The video dataprocessing unit consists of microprocessor CPU's and associatedprocessing chips including high-speed data signal processing (DSP)chips. This unit can format a grid-like or pixel-like pattern that issent to the electrodes by way of the telemetry communication subsystems(118, 121). See FIG. 1 b. In this embodiment of the retinal colorprosthesis (FIG. 1 b, (121)), these electrodes are incorporated in theinternal-to-the eye implanted part.

These electrodes, which are part of the internal implant (121), togetherwith the telemetry circuitry (121) are inside the eye. With otherinternally implanted electronic circuitry (121), they cooperate with theelectrodes so as to replicate the incoming pattern, in a useable form,for stimulation of the retina so as to reproduce a facsimile perceptionof the external scene. The eye-motion (112) and head-motion (131)detectors supply information to the video data processing unit (113) toshift the image presented to the retina (120).

There are three preferred embodiments for stimulating the retina via theelectrodes to convey the perception of color. Color information isacquired by the imaging means (111). The color data is processed in thevideo data processing unit (113).

First Preferred Color Mode

Color information (See FIG. 2 a), in the first preferred embodiment, isencoded by time sequences of pulses (201) separated by varying amountsof time (202), and also with the pulse duration being varied in time(203). The basis for the color encoding is the individual color codereferences (211 through 217). The electrodes stimulate the target cellsso as to create a color image for the patient, corresponding to theoriginal image as seen by the video camera, or other imaging means.Using temporal coding of electrical stimuli placed (cf. FIG. 2 b, 220,FIG. 2 c, 230) on or near the retina (FIG. 2 b and FIG. 2 c, 221, 222)the perception of color can be created in patients blinded by outerretinal degeneration. By sending different temporal coding schemes todifferent electrodes, an image composed of more than one color can beproduced. FIG. 2 shows one stimulation protocol. Cathodic stimuli (202)are below the zero plane (220) and anodic stimuli (203) are above. Allthe stimulus rates are either “fast” (203) or “slow” (202) except forgreen (214), which includes an intermediate stimulus rate (204). Thetemporal codes for the other colors are shown as Red (211), as Magenta(212), as Cyan (213), as Yellow (215), as Blue (216), as Neutral (217).This preferred embodiment is directed toward electrodes which are lessdensely packed in proximity to the retinal cells.

Second Preferred Color Mode

Color information, in a second preferred embodiment, is sent from thevideo data processing unit to the electrode array, where each electrodehas been determined by test to stimulate one of a bipolar type:red-center green-surround, green-center-red-surround,blue-center-yellow-surround, or yellow-center-blue-surround. In thisembodiment, electrodes which are small enough to interact with a singlecell, or at most, a few cells are placed in the vicinity of individualbipolar cells, which react to a stimulus with nerve pulse rates andnerve pulse structure (i.e., pulse duration and pulse amplitude). Someof the bipolar cells, when electrically, or otherwise, stimulated, willsend red-green signals to the brain. Others will send yellow-bluesignals. This refers to the operation of the normal retina. In thenormal retina, red or green color photoreceptors (cone cells) send nervepulses to the red-green bipolar cell which then pass some form of thisinformation up to the ganglion cells and then up to the visual cortex ofthe brain. With small electrodes individual bipolar cells can be excitedin a spatial, or planar, pattern. Small electrodes are those with tipfrom 0.1 μm to 15 μm, and which individual electrodes are spaced apartfrom a range 8 μm to 24 μm, so as to approximate a one-to-onecorrespondence with the bipolar cells. The second preferred embodimentis oriented toward a more densely packed set of electrodes.

Third Preferred Color Mode

A third preferred mode is a combination of the first and of the secondpreferred modes such that a broader area coverage of the colorinformation encoded by time sequences of pulses, of varying widths andseparations and with relatively fewer electrodes is combined with ahigher density of electrodes, addressing more the individual bipolarcells.

First Order and Higher Effects

Regardless of a particular theory of color vision, the impinging ofcolored light on the normal cones, and possibly rods, give rise in somefashion to the perception of color, i.e., multi-spectral vision. In thetime-pulse coding color method, above, the absence of all, orsufficient, numbers of working cones (and rods) suggests ageneralization of the particular time-pulse color encoding method. Thegeneralization is based on the known, or partly known, neuron conductionpathways in the retina. The cone cells, for example, signal to bipolarcells, which in turn signal the ganglion cells. The originalspatial-temporal-color (including black, white) scheme for conveyingcolor information as the cone is struck by particular wavelength photonsis then transformed to a patterned signal firing of the next cellularlevel, say the bipolar cells, unless the cones are absent or don'tfunction. Thus, this second level of patterned signal firing is what onewishes to supply to induce the perception of color vision.

The secondary layer of patterned firing may be close to the necessaryprimary pattern, in which case the secondary pattern (S) may berepresented as P*(1+ε). The * indicates matrix multiplication. P is theprimary pattern, represented as a matrix

$P = \begin{bmatrix}p_{11} & p_{1\; j} \\p_{k\; 1} & p_{kj}\end{bmatrix}$where P represents the light signals of a particular spatial-temporalpattern, e.g., flicker signals for green. The output from the first celllayer, say the cones, is then S, the secondary pattern. This representsthe output from the bipolar layer in response to the input from thefirst (cone) layer. If S=P*(1+ε), where 1 represents a vector and εrepresents a small deviation applied to the vector 1, then S isrepresented by P to the lowest order, and by P*(1+ε) to the next order.Thus, the response may be seen as a zero order effect and a first orderlinear effect. Additional terms in the functional relationship areincluded to completely define the functional relationship. If S is somenon-linear function of P, finding S by starting with P requires moreterms then the linear case to define the bulk of the functionalrelationship. However, regardless of the details of one color visiontheory or another, on physiological grounds S is some function of P. Asin the case of fitting individual patients with lenses for theirglasses, variations of parameters are expected in fitting each patientto a particular temporal coding of electrical stimuli.Scaling Data from Photoreceptors to Bipolar Cells

As cited above, Greenberg (1998), indicates that electrical and photicstimulation of the normal retina operate via similar mechanisms. Thus,even though electrical stimulation of a retina damaged by outer retinaldegeneration is different from the electrical stimulation of a normalretina, the temporal relationships are expected to be analogous.

To explain this, it is noted that electrical stimulation of the normalretinal is accomplished by stimulating the photoreceptor cells(including the color cells activated differentially according to thecolor of light impinging on them). For the outer retinal degeneration,it is precisely these photoreceptor cells which are missing. Therefore,the electrical stimulation in this case proceeds by way of the cellsnext up the ladder toward the optic nerve, namely, the bipolar cells.

The time constant for stimulating photoreceptor is about 20milliseconds. Thus the electrical pulse duration would need to be atleast 20 milliseconds. The time constant for stimulating bipolar cellsis around 9 seconds. These time constants are much longer than for theganglion cells (about 1 millisecond). The ganglion cells are anotherlayer of retinal cells closer to the optic nerve. The actual details ofthe behavior of the different cell types of the retina are quitecomplicated including the different relationships for current thresholdversus stimulus duration (cf. Greenberg, 1998). One may, however,summarize an apparent resonant response of the cells based on their timeconstants corresponding to the actual pulse stimulus duration.

In FIG. 2, which is extrapolated from external-to-the-eye electricalstimulation data of Young (1977) and from light stimulation data ofFestinger, Allyn, and White (1971), there is shown data that would beapplicable to the photoreceptor cells. One may scale the data down basedon the ratio of the photoreceptor time constant (about 20 milliseconds)to that of the bipolar cells (about 9 milliseconds). Consequently, 50milliseconds on the time scale in FIG. 2 now corresponds to 25milliseconds. Advantageously, stimulation rates and duration of pulses,as well as pulse widths may be chosen which apply to the electrodestimulation of the bipolar cells of the retina.

Eye Movement/Head Motion Compensation

In a preferred embodiment, an external imager such as a color CCD orcolor CMOS video camera (111) and a video data processing unit (113),with an external telemetry unit (118) present data to the internaleye-implant part. Another aspect of the preferred embodiment is a methodand apparatus for tracking eye movement (112) and using that informationto shift (113) the image presented to the retina. Another aspect of thepreferred embodiment utilizes a head motion sensor (131) and a headmotion compensation system (131, 113). The video data processing unitincorporates the data of the motion of the eye as well as that of thehead to further adjust the image electronically so as to account for eyemotion and head motion. Thus electronic image compensation,stabilization and adjustment are provided by the eye and head movementcompensation subsystems of the external part of the retinal colorprosthesis.

Logarithmic Encoding of Light

In one aspect of an embodiment (FIG. 1 b), light amplitude is recordedby the external imager (111). The video data processing unit uses alogarithmic encoding scheme (113) to convert the incoming lightamplitudes into the logarithmic electrical signals of these amplitudes(113). These electrical signals are then passed on by telemetry (118),(121), to the internal implant (121) which results in the retinal cells(120) being stimulated via the implanted electrodes (121), in thisembodiment as part of the internal implant (121). Encoding is doneoutside the eye, but may be done internal to the eye, with a sufficientinternal computational capability.

Energy and Signal Transmission

Coils

The retinal prosthesis system contains a color imager (FIG. 1 b, 111)such as a color CCD or CMOS video camera. The imaging output data istypically processed (113) into a pixel-based format compatible with theresolution of the implanted system. This processed data (113) is thenassociated with corresponding electrodes and amplitude and pulse-widthand frequency information is sent by telemetry (118) into the internalunit coils, (311), (313), (314) (see FIG. 3 a). Electromagnetic energy,is transferred into and out from an electronic component (311) locatedinternally in the eye (312), using two insulated coils, both locatedunder the conjunctiva of the eye with one free end of one coil (313)joined to one free end of the second coil (314), the second free end ofsaid one coil joined to the second free end of said second coil. Thesecond coil (314) is located in proximity to a coil (311) which is apart of said internally located electronic component, or, directly tosaid internally located electronic component (311). The larger coil ispositioned near the lens of the eye. The larger coil is fastened inplace in its position near the lens of the eye, for example, bysuturing. FIG. 3 b represents an embodiment of the telemetry unittemporally located near the eye, including an external temporal coil(321), an internal (to the eye) coil (314), an external-to-the-eyeelectronic chip (320), dual coil transfer units (314, 323), (321,322)and an internal-to-the-eye electrode array (325). The advantage oflocating the external electronics in the fatty tissue behind the eye isthat there is a reasonable amount of space there for the electronics andin that position it appears not to interfere with the motion of the eye.

Ultrasonic Sound

In another aspect the information coding is done with ultrasonic soundand in a third aspect information is encoded by modulating light. An(FIG. 3 c) ultrasonic transducer (341) replaces the electromagnetic wavereceiving coil on the implant (121) inside the eye. An ultrasonictransducer (342) replaces the coil outside the eye for the ultrasoniccase. A transponder (343) under the conjunctiva of the eye may be usedto amplify the acoustic signal and energy either direction. Bypiezoelectric effects, the sound vibration is turned into electricalcurrent, and energy extracted therefrom.

Modulated Light Beam

For the light modulation (FIG. 3 d) case, a light emitting diode (LED)or laser diode or other light generator (361), capable of beingmodulated, acts as the information transmitter. Information istransferred serially by modulating the light beam, and energy isextracted from the light signal after it is converted to electricity. Aphoto-detector (362), such as a photodiode, which turns the modulatedlight signal into a modulated electrical signal, is used as a receiver.A set of a photo-generator and a photo-detector are on the implant (121)and a set is also external to the eye

Prototype-Like Device

FIG. 4 show an example of the internal-to-the-eye and theexternal-to-the eye parts of the retinal color prosthesis, together witha means for communicating between the two. The video camera (401)connects to an amplifier (402) and to a microprocessor (403) with memory(404). The microprocessor is connected to a modulator (405). Themodulator is connected to a coil drive circuit (406). The coil drivecircuit is connected to an oscillator (407) and to the coil (408). Thecoil (408) can receive energy inductively, which can be used to rechargea battery (410), which then supplies power. The battery may also berecharged from a charger (409) on a power line source (411).

The internal-to-the eye implanted part shows a coil (551), whichconnects to both a rectifier circuit (552) and to a demodulator circuit(553). The demodulator connects to a switch control unit (554). Therectifier (552) connects to a plurality of diodes (555) which rectifythe current to direct current for the electrodes (556); the switchcontrol sets the electrodes as on or off as they set the switches (557).The coils (408) and (551) serve to connect inductively theinternal-to-the-eye (500) subsystem and the external-to-the patient(400) subsystem by electromagnetic waves. Both power and information canbe sent into the internal unit. Information can be sent out to theexternal unit. Power is extracted from the incoming electromagneticsignal and may be accumulated by capacitors connected to each electrodeor by capacitive electrodes themselves.

Simple Electrode Implant

FIG. 6 a illustrates a set of round monopolar electrodes (602) on asubstrate material (601). FIG. 7 shows the corresponding indifferentelectrode (702) for these monopolar electrodes, on a substrate (701),which may be the back of (601). FIG. 6 b shows a bipolar arrangement ofelectrodes, both looking down onto the plane of the electrodes, positive(610) and negative (611), and also looking at the electrodes sideways tothat view, positive (610) and negative (611), sitting on their substrate(614). Similarly for FIG. 6 c where a multipole triplet is shown, withtwo positive electrodes (621) and one negative electrode, looking downon their substrate plane, and looking sideways to that view, alsoshowing the substrate (614).

Epiretinal Electrode Array

FIG. 8 a depicts the location of an epiretinal electrode array (811)located inside the eye (812) in the vitreous humor (813) located abovethe retina (814), toward the lens capsule (815) and the aqueous humor(816);

One aspect of the present embodiment, shown in FIG. 8 b, is the internalretinal color prosthetic part, which has electrodes (817) which may beflat conductors that are recessed in an electrical insulator (818). Oneflat conductor material is a biocompatible metallic foil (817). Platinumfoil is a particular type of biocompatible metal foil. The electricalinsulator (818) in one aspect of the embodiment is silicone.

The silicone (818) is shaped to the internal curvature of the retina(814). The vitreous humor (813), the conductive solution naturallypresent in the eye, becomes the effective electrode since the insulator(818) confines the field lines in a column until the current reaches theretina (814). A further advantage of this design is that the retinaltissue (814) is only in contact with the insulator (818), such assilicone, which may be more inactive, and thus, more biocompatible thanthe metal in the electrodes. Advantageously, another aspect of anembodiment of this invention is that adverse products produced by theelectrodes (817) are distant from the retinal tissue (814) when theelectrodes are recessed.

FIG. 8 c shows elongated epiretinal electrodes (820). The electricallyconducting electrodes (820) says are contained within the electricalinsulation material (818); a silicon chip (819) acts as a substrate. Theelectrode insulator device (818) is shaped so as to contact the retina(814) in a conformal manner.

Subretinal Electrode Array

FIG. 9 a shows the location of a subretinal electrode array (811) belowthe retina (814), away from the lens capsule (815) and the aqueous humor(816). The retina (814) separates the subretinal electrode array fromthe vitreous humor (813). FIG. 9 b illustrates the subretinal electrodearray (811) with pointed elongated electrodes (817), the insulator(818), and the silicon chip (819) substrate. The subretinal electrodearray (811) is in conformal contact with the retina (814) with theelectrodes (817) elongated to some depth.

Electrodes

Iridium Electrodes

Now FIG. 10 will illuminate structure and manufacture of iridiumelectrodes (FIGS. 10 a-e). FIG. 10 a shows an iridium electrode, whichcomprises an iridium slug (1011), an insulator (1012), and a devicesubstrate (1013). This embodiment shows the iridium slug electrode flushwith the extent of the insulator. FIG. 10 b indicates an embodimentsimilar to that shown in FIG. 10 a, however, the iridium slug (1011) isrecessed from the insulator (1012) along its sides, but with its topflush with the insulator. When the iridium electrodes (1011) arerecessed in the insulating material (1012), they may have the sidesexposed so as to increase the effective surface area without increasinggeometric area of the face of the electrode. If an electrode (1011) isnot recessed it may be coated with an insulator (1012), on all sides,except the flat surface of the face (1011) of the electrode. Such anarrangement can be embedded in an insulator that has an overall profilecurvature that follows the curvature of the retina. The overall profilecurvature may not be continuous, but may contain recesses, which exposethe electrodes.

FIG. 10 c shows an embodiment with the iridium slug as in FIG. 10 b,however, the top of the iridium slug (1011) is recessed below the levelof the insulator; FIG. 10 d indicates an embodiment with the iridiumslug (1011) coming to a point and insulation along its sides (1021), aswell as a being within the overall insulation structure (1021). FIG. 10e indicates an embodiment of a method for fabricating the iridiumelectrodes. On a substrate (1013) of silicon, an aluminum pad (1022) isdeposited. On the pad the conductive adhesive (1023) is laid andplatinum or iridium foil (1024) is attached thereby. A titanium ring(1025) is placed, sputtered, plated, ion implanted, ion beam assisteddeposited (IBAD) or otherwise attached to the platinum or iridium foil(1024). Silicon carbide, diamond-like coating, silicon nitride andsilicon oxide in combination, titanium oxide, tantalum oxide, aluminumnitride, aluminum oxide or zirconium oxide (1012) or other insulator canadhere better to the titanium (1025) while it would not otherwise adhereas well to the platinum or iridium foil (1024). The depth of the wellfor the iridium electrodes ranges from 0.1 μm to 1 mm.

Elongated Electrode

Another aspect of an embodiment of the invention is the elongatedelectrode, which are designed to stimulate deeper retinal cells, in oneembodiment, by penetrating the retina. By getting closer to the targetcells for stimulation, the current required for stimulation is lower andthe focus of the stimulation is more localized. The lengths chosen are100 microns through 500 microns, including 300 microns. FIG. 8 c is arendering of an elongated epiretinal electrode array with the electrodesshown as pointed electrical conductors (820), embedded in an electricalinsulator (818), where the elongated electrodes (817) contact the retinain a conformal manner, however, penetrating into the retina (814).

These elongated electrodes, in an aspect of this of an embodiment of theinvention may be of all the same length. In a different aspect of anembodiment, they may be of different lengths. Said electrodes may be ofvarying lengths (FIG. 8, 817), such that the overall shape of saidelectrode group conforms to the curvature of the retina (814). In eitherof these cases, each may penetrate the retina from an epiretinalposition (FIG. 8 a, 811), or, in a different aspect of an embodiment ofthis invention, each may penetrate the retina from a subretinal position(FIG. 9 b, 817).

One method of making the elongated electrodes is by electroplating withone of an electrode material, such that the electrode, after beingstarted, continuously grows in analogy to a stalagmite or stalactite.The elongated electrodes are 100 to 500 microns in length, the thicknessof the retina averaging 200 microns. The electrode material is asubstance selected from the group consisting of pyrolytic carbon,titanium nitride, platinum, iridium oxide, and iridium. The insulatingmaterial for the electrodes is a substance selected from the groupsilicon carbide, diamond-like coating, silicon nitride and silicon oxidein combination, titanium oxide, tantalum oxide, aluminum nitride,aluminum oxide or zirconium oxide.

Platinum Electrodes

FIGS. 11 (a-e) demonstrates a preferred structure of, and method of,making, spiked and mushroom platinum electrodes. Examining FIG. 11 a onesees that the support for the flat electrode (1103) and other componentssuch as electronic circuits (not shown) is the silicon substrate (1101).An aluminum pad (1102) is placed where an electrode or other componentis to be placed. In order to hermetically seal-off the aluminum andsilicon from any contact with biological activity, a metal foil (1103),such as platinum or iridium, is applied to the aluminum pad (1102) usingconductive adhesive (1104). Electroplating is not used since a layerformed by electroplating, in the range of the required thinness, hassmall-scale defects or holes which destroy the hermetic character of thelayer. A titanium ring (1105) is next placed on the platinum or iridiumfoil (1103). Normally, this placement is by ion implantation, sputteringor ion beam assisted deposition (IBAD) methods. Silicon carbide,diamond-like coating, silicon nitride and silicon oxide in combination,titanium oxide, tantalum oxide, aluminum nitride, aluminum oxide orzirconium oxide (1106) is placed on the silicon substrate (1101) and thetitanium ring (1105). In one embodiment, an aluminum layer (1107) isplated onto exposed parts of the titanium ring (1105) and onto thesilicon carbide, diamond-like coating, silicon nitride and silicon oxidein combination, titanium oxide, tantalum oxide, aluminum nitride,aluminum oxide or zirconium oxide (1106). In this embodiment thealuminum (1107) layer acts as an electrical conductor. A mask (1108) isplaced over the aluminum layer (1107).

In forming an elongated, non-flat, electrode (FIG. 11 b), platinum iselectroplated onto the platinum or iridium foil (1103). Subsequently,the mask (1108) is removed and insulation (1110) is applied over theplatinum electrode (1109).

In FIG. 11 c, a platinum electrode (1109) is shown which is moreinternal to the well formed by the silicon carbide, diamond-likecoating, silicon nitride and silicon oxide in combination, titaniumoxide, tantalum oxide, aluminum nitride, aluminum oxide or zirconiumoxide and its titanium ring. The electrode (1109) is also thinner andmore elongated and more pointed. FIG. 11 d shows a platinum electrodeformed by the same method as was used in FIGS. 11 a, 11 b, and 11 c. Theplatinum electrode (1192) is more internal to the well formed by thesilicon carbide, diamond-like coating, silicon nitride and silicon oxidein combination, titanium oxide, tantalum oxide, aluminum nitride,aluminum oxide or zirconium oxide and its titanium ring as was theelectrode (1109) in FIG. 11 c. However it is less elongated and lesspointed.

The platinum electrode is internal to the well formed by the siliconcarbide, diamond-like coating, silicon nitride and silicon oxide incombination, titanium oxide, tantalum oxide, aluminum nitride, aluminumoxide or zirconium oxide and its titanium ring; said electrode wholeangle at it's peak being in the range from 1° to 120°; the base of saidconical or pyramidal electrode ranging from 1 micron to 500 micron; thelinear section of the well unoccupied by said conical or pyramidalelectrode ranging from zero to one-third.

A similar overall construction is depicted in FIG. 11 e. The electrode(1193), which may be platinum, is termed a mushroom shape. The maximumcurrent density for a given metal is fixed. The mushroom shape presentsa relatively larger area than a conical electrode of the same height.The mushroom shape advantageously allows a higher current, for the givenlimitation on the current density (e.g., milliamperes per squaremillimeter) for the chosen electrode material, since the mushroom shapeprovides a larger area.

Inductive Coupling Coils

Information transmitted electromagnetically into or out of the implantedretinal color prosthesis utilizes insulated conducting coils so as toallow for inductive energy and signal coupling. FIG. 12 b shows aninsulated conducting coil and insulated conducting electrical pathways,e.g., wires, attached to substrates at what would otherwise be electrodenodes, with flat, recessed metallic, conductive electrodes (1201). Inreferring to wire or wires, insulated conducting electrical pathways areincluded, such as in a “two-dimensional” “on-chip” coil or a“two-dimensional” coil on a polyimide substrate, and the leads to andfrom these “two-dimensional” coil structures. A silicon carbide,diamond-like coating, silicon nitride and silicon oxide in combination,titanium oxide, tantalum oxide, aluminum nitride, aluminum oxide orzirconium oxide (1204) is shown acting as both an insulator and anhermetic seal. Another aspect of the embodiment is shown in FIG. 12 d.The electrode array unit (1201) and the electronic circuitry unit (1202)can be on one substrate, or they may be on separate substrates (1202)joined by an insulated wire or by a plurality of insulated wires (1203).Said separate substrate units can be relatively near one another. Forexample, they might lie against a retinal surface, either epiretinallyor subretinally placed. Two substrates units connected by insulatedwires may carry more electrodes than if only one substrate withelectrodes was employed, or it might be arranged with one substratecarrying the electrodes, the other the electronic circuitry. Anotherarrangement has the electrode substrate or substrates placed in aposition to stimulate the retinal cells, while the electronics arelocated closer to the lens of the eye to avoid heating the sensitiveretinal tissue.

In all of the FIGS. 12 a, 12 b, and 12 c, a coil (1205) is shownattached by an insulated wire. The coil can be a coil of wire, or it canbe a “two dimensional” trace as an “on-chip” component or as a componenton polyimide. This coil can provide a stronger electromagnetic couplingto an outside-the-eye source of power and of signals. FIG. 12 c shows anexternally placed aluminum (conductive) trace instead of theelectrically conducting wire of FIG. 12 d. Also shown is an electricallyinsulating adhesive (1208) which prevents electrical contact between thesubstrates (1202) carrying active circuitry (1209).

Hermetic Sealing

Hermetic Coating

All structures, which are subject to corrosive action as a result ofbeing implanted in the eye, or, those structures which are notcompletely biocompatible and not completely safe to the internal cellsand fluids of the eye require hermetic sealing. Hermetic sealing may beaccomplished by coating the object to be sealed with silicon carbide,diamond-like coating, silicon nitride and silicon oxide in combination,titanium oxide, tantalum oxide, aluminum nitride, aluminum oxide orzirconium oxide. These materials also provide electrical insulation. Themethod and apparatus of hermetic sealing by aluminum and zirconium oxidecoating is described in a pending U.S. patent application Ser. No.08/994,515, now U.S. Pat. No. 6,043,437. The methods of coating asubstrate material with the hermetic sealant include sputtering, ionimplantation, and ion-beam assisted deposition (IBAD).

Hermetic Box

Another aspect of an embodiment of the invention is hermetically sealingthe silicon chip (1301) by placing it in a metal or ceramic box (1302)of rectangular cross-section with the top and bottom sides initiallyopen (FIG. 13). The box may be of one (1302) of the metals selected fromthe group comprising platinum, iridium, palladium, gold, and stainlesssteel. Solder balls (1303) are placed on the “flip-chip”, i.e., asilicon-based chip that has the contacts on the bottom of the chip(1301). Metal feedthroughs (1304) made from a metal selected from thegroup consisting of radium, platinum, titanium, iridium, palladium,gold, and stainless steel. The bottom cover (1306) is formed from one ofthe ceramics selected from the group consisting of aluminum oxide orzirconium oxide. The inner surface (1305), toward the solder ball,(1303)) of the feed-through (1304) is plated with gold or with nickel.The ceramic cover (1306) is then attached to the box using a braze(1307) selected from the group consisting of: 50% titanium together with50% nickel and gold. Electronics are then inserted and the metal topcover (of the same metal selected for the box) is laser welded in place.

Separate Electronics Chip Substrate and Electrode Substrate

In one embodiment of the invention (FIG. 14), the chip substrate (1401)is hermetically sealed in a case (1402) or by a coating of the aluminum,zirconium, or magnesium oxide coating. However, the electrodes (1403)and its substrate (1404) form a distinct and separate element. Insulatedand hermetically sealed wires (1405) connect the two. The placement ofthe electrode element may be epiretinal, while the electronic chipelement may be relatively distant from the electrode element, as muchdistant as being in the vicinity of the eye lens. Another embodiment ofthe invention has the electrode element placed subretinally and theelectronic chip element placed toward the rear of the eye, being outsidethe eye, or, being embedded in the sclera of the eye or in or under thechoroid, blood support region for the retina. Another embodiment of theinvention has the electronic chip element implanted in the fatty tissuebehind the eye and the electrode element placed subretinally orepiretinally.

Capacitive Electrodes

A plurality of capacitive electrodes can be used to stimulate theretina, in place of non-capacitive electrodes. A method of fabricatingsaid capacitive electrode uses a pair of substances selected from thepair group consisting of the pairs iridium and iridium oxide; and,titanium and titanium nitride. The metal electrode acts with theinsulating oxide or nitride, which typically forms of its own accord onthe surface of the electrode. Together, the conductor and the insulatorform an electrode with capacitance.

Mini-capacitors (FIG. 15) can also be used to supply the requiredisolating capacity. The capacity of the small volume size capacitors(1501) is 0.47 microfarads. The dimensions of these capacitors areindividually 20 mils (length) by 20 mils (width) by 40 mils (height). Inone embodiment of the invention, the capacitors are mounted on thesurface of a chip substrate (1502), that surface being opposite to thesurface containing the active electronics elements of the chipsubstrate.

Electrode/Electronics Component Placement

In one embodiment (FIG. 16 a), the internal-to-the-eye implanted partconsists of two subsystems, the electrode component subretinallypositioned and the electronic component epiretinally positioned. Theelectronics component, with its relatively high heat dissipation, ispositioned at a distance, within the eye, from the electrode componentplaced near the retina that is sensitive to heat.

An alternative embodiment shown in FIG. 16 b is where one of thecombined electronic and electrode substrate units is positionedsubretinally and the other is located epiretinally and both are heldtogether across the retina so as to efficiently stimulate bipolar andassociated cells in the retina.

An alternative embodiment of the invention has the electronic chipelement implanted in the fatty tissue behind the eye and the electrodeelement placed subretinally or epiretinally, and power and signalcommunication between them by electromagnetic means includingradio-frequency (RF), optical, and quasi-static magnetic fields, or byacoustic means including ultrasonic transducers.

FIG. 16 c shows how the two electronic-electrode substrate units areheld positioned in a prescribed relationship to each other by smallmagnets. Alternatively the two electronic-electrode substrate units areheld in position by alignment pins. Another aspect of this is to havethe two electronic-electrode substrate units held positioned in aprescribed relationship to each other by snap-together mating parts,some exemplary ones being shown in FIG. 16 d.

Neurotrophic Factor

Another aspect of the embodiment is the use of a neurotrophic factor,for example, Nerve Growth Factor, applied to the electrodes, or to thevicinity of the electrodes, to aid in attracting target nerves and othernerves to grow toward the electrodes.

Eye-Motion Compensation System

Another aspect of the embodiment is an eye-motion compensation systemcomprising an eye-movement tracking apparatus (FIG. 1 b, 112);measurements of eye movement; a transmitter to convey said measurementsto video data processor unit that interprets eye movement measurementsas angular positions, angular velocities, and angular accelerations; andthe processing of eye position, velocity, acceleration data by the videodata processing unit for image compensation, stabilization andadjustment.

Ways of eye-tracking (FIG. 1 b, 112) include utilizing the corneal eyereflex, utilizing an apparatus for measurements of electrical activitywhere one or more coils are located on the eye and one or more coils areoutside the eye, utilizing an apparatus where three orthogonal coilsplaced on the eye and three orthogonal coils placed outside the eye,utilizing an apparatus for tracking movements where electricalrecordings from extra-ocular muscles are measured and conveyed to thevideo data processing unit that interprets such electrical measurementsas angular positions, angular velocities, and angular accelerations. Thevideo data processing unit uses these values for eye position, velocity,acceleration to compute image compensation, stabilization and adjustmentdata which is then applied by the video data processor to the electronicform of the image.

Head Sensor

Another aspect of the embodiment utilizes a head motion sensor (131).The basic sensor in the head motion sensor unit is an integratingaccelerometer. A laser gyroscope can also be used. A third sensor is thecombination of an integrating accelerometer and a laser gyroscope. Thevideo data processing unit can incorporate the data of the motion of theeye as well as that of the head to further adjust the imageelectronically so as to account for eye motion and head motion.

Physician's Local Control Unit

Another aspect includes a retinal prosthesis with (see FIG. 1 b) aphysician's local external control unit (115) allowing the physician toexert setup control of parameters such as amplitudes, pulse widths,frequencies, and patterns of electrical stimulation. The physician'scontrol unit (115) is also capable of monitoring information from theimplanted unit (121) such as electrode current, electrode impedance,compliance voltage, and electrical recordings from the retina. Themonitoring is done via the internal telemetry unit, electrode andelectronics assembly (121).

An important aspect of setting up the retinal color prosthesis issetting up electrode current amplitudes, pulse widths, and frequenciesso they are comfortable for the patient. FIGS. 17 a-c and FIGS. 18 a-cillustrate some of the typical displays. A computer-controlledstimulating test that incorporates patient response to arrive at optimalpatient settings may be compared to being fitted for eyeglasses, firstdetermining diopter, then cylindrical astigmatic correction, and soforth for each patient. The computer uses interpolation andextrapolation routines. Curve or surface or volume fitting of data maybe used. For each pixel, the intensity in increased until a threshold isreached and the patient can detect something in his visual field. Theintensity is further increased until the maximum comfortable brightnessis reached. The patient determines his subjective impression ofone-quarter maximum brightness, one-half maximum brightness, andthree-quarters maximum brightness. Using the semi-automated processingof the patient-in-the-loop with the computer, the test program runsthrough the sequences and permutations of parameters and remembers thepatient responses. In this way apparent brightness response curves arecalibrated for each electrode for amplitude. Additionally, in the sameway as for amplitude, pulse width and pulse rate (frequency), responsecurves are calibrated for each patient. The clinician can then determinewhat the best settings are for the patient.

This method is generally applicable to many, if not all, types ofelectrode based retinal prostheses. Moreover, it also is applicable tothe type of retinal prosthesis, which uses an external light intensifiershining upon essentially a spatially distributed set of light sensitivediodes with a light activated electrode. In this latter case, aphysician's test, setup and control unit is applied to the lightintensifier which scans the implanted photodiode array, element byelement, where the patient can give feedback and so adjust the lightintensifier parameters.

Remote Physician's Unit

Another aspect of an embodiment of this invention includes (see FIG. 1b) a remote physician control unit (117) that can communicate with apatient's unit (114) over the public switched telephone network or othertelephony means. This telephone-based pair of units is capable ofperforming all of the functions of the of the physician's local controlunit (115).

Physician's Unit Measurements, Menus and Displays

Both the physician's local (115) and the physician's remote (117) unitsalways measure brightness, amplitudes, pulse widths, frequencies,patterns of stimulation, shape of log amplification curve, electrodecurrent, electrode impedance, compliance voltage and electricalrecordings from the retina.

FIG. 17 a shows the main screen of the Physician's Local and RemoteController and Programmer. FIG. 17 b illustrates the pixel selection ofthe processing algorithm with the averaging of eight surrounding pixelschosen as one element of the processing. FIG. 17 c represents anelectrode scanning sequence, in this case the predefined sequence, A.FIG. 17 d shows electrode parameters, here for electrode B, includingcurrent amplitudes and waveform timelines. FIG. 17 e illustrates thescreen for choosing the global electrode configuration, monopolar,bipolar, or multipolar. FIG. 17 f renders a screen showing thedefinition of bipolar pairs (of electrodes). FIG. 17 g shows thedefinition of the multipole arrangements.

FIG. 18 a illustrates the main menu screen for the palm-sized test unit.FIG. 18 b shows a result of pressing on the stimulate bar of the(palm-sized unit) main menu screen, where upon pressing the start buttonthe amplitudes A1 and A2 are stimulated for times t1, t2, t3, and t4,until the stop button is pressed. FIG. 18 c exhibits a recording screenthat shows the retinal recording of the post-stimulus and the electrodeimpedance.

FIGS. 19 a, 19 b, and 19 c show different embodiments of the Physician'sRemote Controller, which has the same functionality inside as thePhysician's Local Controller but with the addition of communicationmeans such as telemetry or telephone modem.

Patient's Controller

Corresponding to the Physician's Local Controller, but with much lesscapability, is the Patient's Controller. FIG. 20 shows the patient'slocal controller unit. This unit can monitor and adjust brightness(2001), contrast (2002) and magnification (2003) of the image on anon-continuous basis. The magnification control (2003) adjustsmagnification both by optical zoom lens control of the lens for theimaging means (FIG. 1, 111), and by electronic adjustment of the imagein the data processor (FIG. 2, 113).

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims.

We claim:
 1. An implantable system comprising: an external coil,suitable to be outside a living body; a repeating coil pair, suitable tobe implanted within the living body, wherein a first coil is within aninductive field of said external coil, and is electrically coupled to anamplifier which is electrically coupled to a second coil within aninductive field of a device coil; and an implantable device, includingsaid device coil; wherein energy is transmitted from said external coilto said first coil, then to said second coil, then to said device coilto power said implantable device.
 2. The implantable system according toclaim 1, wherein said repeating coil pair is suitable to be implantedinternal to a living body and external to an eye.
 3. The implantablesystem according to claim 2, wherein said first coil is suitable to benear the front of an eye and said second coil is suitable to be near aretina.
 4. The implantable system according to claim 3, wherein saiddevice coil is suitable to be internal to the eye.
 5. The implantablesystem according to claim 1, wherein said external coil is foamed withina pair of glasses.